BROOKLYN PARK, Minn. — Minnesota’s state butterfly is elusive.

Scientists say the population of Monarch butterflies has crashed because of extreme weather in southern states. The butterflies migrate north from Mexico as the weather warms during the summer and leave by about mid-August. Experts say Monarchs need a temperature of 55 degrees to fly.

Elizabeth Howard directs the Monarch research group Journey North. Howard tells Minneosota Public Radio News (http://bit.ly/172mF0Q ) that milkweed plants weren’t far enough along in Texas because of a cold spring, so the butterflies couldn’t lay eggs. The milkweed is the only plant in which the Monarchs will lay eggs. She says a generation of Monarchs may have been lost.

In Minnesota, sightings of the summer visitor, with its familiar black and orange wings, are rare.